// Copyright (C) 2024 Kumo inc.
// Author: Jeff.li lijippy@163.com
// All rights reserved.
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published
// by the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.
//

#include <iostream>

#include <deneb/lru.h>

using Cache = deneb::Cache<std::uint64_t, std::uint64_t>;

std::uint64_t fibonacci(std::uint64_t n, Cache& cache) {
  if (n < 2) return 1;

  // We std::uint64_ternally keep track of the last accessed key, meaning a
  // `contains(key)` + `lookup(key)` sequence will involve only a single hash
  // table lookup.
  if (cache.contains(n)) return cache[n];

  auto value = fibonacci(n - 1, cache) + fibonacci(n - 2, cache);

  // Caches are 100% move-aware and we have implemented
  // `unordered_map` style emplacement and insertion.
  cache.emplace(n, value);

  return value;
}

std::uint64_t fibonacci(std::uint64_t n) {
  // Use a capacity of 100 (after 100 insertions, the next insertion will evict
  // the least-recently inserted element). The default capacity is 128. Note
  // that for fibonacci, a capacity of 2 is sufficient (and ideal).
  Cache cache(100);
  cache.monitor(2, 3, 4, 5);
  auto value = fibonacci(n, cache);

  for (auto i : {2, 3, 4, 5}) {
    auto stats = cache.stats().stats_for(i);
    // clang-format off
    std::cout << "Statistics for " << i << ": "
              << stats.hits << " hit(s), "
              << stats.misses << " miss(es)."
              << std::endl;
  }

  // You'll notice we'll always have n - 1 misses, for each time we access
  // one of the numbers in [0, n] for the first time.
  std::cout << "Overall: "
            << cache.stats().total_hits() << " hit(s), "
            << cache.stats().total_misses() << " miss(es)."
            << std::endl;
  // clang-format on

  return value;
}

auto main() -> int {
  // The last number that fits into a 64 bit unsigned number
  std::cout << fibonacci(92) << std::endl;
}
